The Fayetteville Flora I: Upper Mississippian (middle Chesterian/lower Namurian A) plant assemblages of permineralized and compression remains from Arkansas, USA

The Fayetteville Formation of northwestern Arkansas contains a unique Upper Mississippian fossil flora with allochthonous permineralized plant remains recovered from offshore marine black shales and two coalified compression assemblages: one compression assemblage represents an autochthonous terrestrial/deltaic assemblage, and the other was recovered from near-shore strata. Fossil plants have been known from the Fayetteville Formation since at least 1937, and since that time, numerous individual taxa have been described, but no synopsis of the assemblages has been previously complied. This report summarizes previous reports and adds new data to produce a comprehensive floristic survey of this important fossil flora. The flora consists of 41 morphospecies: 19 permineralized species and 22 compression species that represent at least 15 whole plants. Lycopsid remains are the most numerous and pteridosperms are the most diverse. Sphenopsids are abundant but of low diversity (one genus) and ferns are rare. Lyginopteris royalii, Trivena arkansana, Megaloxylon wheelerae, Quaestora amplecta, Rhynchosperma quinnii, Chlamidostachys chesterianus, and Telangiopsis arkansanum are known only from these strata. The occurrence of Rhetinangium marks the first report of this genus in North America, and the occurrence of Medullosa is the oldest unequivocal evidence for this genus anywhere in the world. (C) 2004 Elsevier B.V. All rights reserved.